Silvicultural Practices as Main Drivers of the Spread of Tree of Heaven (Ailanthus altissima (Mill.) Swingle) ^†

The impacts of anthropogenic disturbances on the spread of invasive species is one of the central issues of invasion biology. In our study, we aimed to investigate the relationship between certain silvicultural activities and the spread of Tree of Heaven (Ailanthus altissima) in calcareous sand forests (Peszéri-erdő, Central Hungary). We applied full-cover mapping (25 × 25 m grid) and BACI design to monitor the effects of clear-cuttings and selective thinnings on the prevalence and abundance of A. altissima in several stands (in total 26 ha). We also investigated young and middle-aged artificial reforestations (4 to 26 yrs.), where stump deposits were made (in total 30 ha). Our results indicate that silvicultural practices may significantly contribute to the spread of A. altissima. One or two years after the accomplishment of selective thinning or clear-cutting, the increase in both the small-scale prevalence and the total abundance of A. altissima was significantly higher compared to control stands. Stump deposits proved to be deterministic in the spread of A. altissima. A decrease in the abundance of A. altissima was observable only in one forest stand where verticillium wilt infection was detected, indicating a biological opportunity to control the spread of A. altissima.